Articles and methods for bonding sheets with carriers

ABSTRACT

Described herein are organosilicon modification layers and associated deposition methods and inert gas treatments that may be applied on a sheet, a carrier, or both, to control van der Waals, hydrogen and covalent bonding between a sheet and carrier. The modification layers bond the sheet and carrier together such that a permanent bond is prevented at high temperature processing as well as maintaining a sufficient bond to prevent delamination during high temperature processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/574,560 filed on Nov. 16, 2017, which claims the benefit of priorityunder 35 U.S.C. § 371 of International Patent Application Serial No.PCT/US2016/032843, filed on May 17, 2016, which in turn, claims thebenefit of priority of U.S. Provisional Patent Application Ser. No.62/201,245 filed on Aug. 5, 2015 and U.S. Provisional Patent ApplicationSer. No. 62/163,821 filed on May 19, 2015, the contents of each of whichare relied upon and incorporated herein by reference in theirentireties.

FIELD

The present disclosure relates generally to articles and methods forprocessing sheets on carriers and, more particularly, to articles andmethods for processing flexible glass sheets on glass carriers.

BACKGROUND

Flexible substrates offer the promise of cheaper devices usingroll-to-roll processing, and the potential to make thinner, lighter,more flexible and durable displays. However, the technology, equipment,and processes required for roll-to-roll processing of high qualitydisplays are not yet fully developed. Since panel makers have alreadyheavily invested in toolsets to process large sheets of glass,laminating a flexible substrate to a carrier and making display devicesby sheet-to-sheet processing offers a shorter term solution to developthe value proposition of thinner, lighter, and more flexible displays.Displays have been demonstrated on polymer sheets for examplepolyethylene naphthalate (PEN) where the device fabrication wassheet-to-sheet with the PEN laminated to a glass carrier. The uppertemperature limit of the PEN limits the device quality and process thatcan be used. In addition, the high permeability of the polymer substrateleads to environmental degradation of organic light emitting diode(OLED) devices where a near hermetic package is required. Thin filmencapsulation offers the promise to overcome this limitation, but it hasnot yet been demonstrated to offer acceptable yields at large volumes.

In a similar manner, display devices can be manufactured using a glasscarrier laminated to one or more thin glass substrates. It isanticipated that the low permeability and improved temperature andchemical resistance of the thin glass will enable higher performancelonger lifetime flexible displays.

The concept involves bonding a thin sheet, for example, a flexible glasssheet, to a carrier initially by van der Waals forces, then increasingthe bond strength in certain regions while retaining the ability toremove portions of the thin sheet after processing the thinsheet/carrier to form devices (for example, electronic or displaydevices, components of electronic or display devices, OLED materials,photo-voltaic (PV) structures, or thin film transistors (TFTs), thereon.At least a portion of the thin glass is bonded to a carrier such thatthere is prevented device process fluids from entering between the thinsheet and carrier, whereby there is reduced the chance of contaminatingdownstream processes, i.e., the bonded seal portion between the thinsheet and carrier is hermetic, and in some preferred embodiments, thisseal encompasses the outside of the article thereby preventing liquid orgas intrusion into or out of any region of the sealed article.

In low temperature polysilicon (LTPS) device fabrication processes, forexample with temperatures approaching 600° C. or greater, vacuum, andwet etch environments may be used. These conditions limit the materialsthat may be used, and place high demands on the carrier/thin sheet.Accordingly, what is desired is a carrier approach that utilizes theexisting capital infrastructure of the manufacturers, enables processingof thin glass, i.e., glass having a thickness ≤0.3 millimeters (mm)thick, without contamination or loss of bond strength between the thinglass and carrier at higher processing temperatures, and wherein thethin glass de-bonds easily from the carrier at the end of the process.

One commercial advantage is that manufacturers will be able to utilizetheir existing capital investment in processing equipment while gainingthe advantages of the thin glass sheets for PV, OLED, liquid crystaldisplays (LCDs) and patterned TFT electronics, for example.Additionally, such an approach enables process flexibility, including:processes for cleaning and surface preparation of the thin glass sheetand carrier to facilitate bonding; processes for strengthening the bondbetween the thin sheet and carrier at the bonded area; processes formaintaining releasability of the thin sheet from the carrier at acontrollably bonded (or reduced/low-strength bond) area; and processesfor cutting the thin sheets to facilitate extraction from the carrier.

In the glass-to-glass bonding process, the glass surfaces are cleaned toremove all metal, organic and particulate residues, and to leave amostly silanol terminated surface. The glass surfaces are first broughtinto intimate contact, where van der Waals and/or Hydrogen-bondingforces pull them together. With heat and optionally pressure, thesurface silanol groups can condense to form strong covalent Si—O—Sibonds across the interface, permanently fusing the glass pieces. Metal,organic and particulate residue will prevent bonding by obscuring thesurface, thereby preventing the intimate contact required for bonding. Ahigh silanol surface concentration is also required to form a strongbond, as the number of bonds per unit area will be determined by theprobability of two silanol species on opposing surfaces reacting tocondense out water. Zhuravlev has reported the average number ofhydroxyls per nm² for well hydrated silica as 4.6 to 4.9. Zhuravlev, L.T., The Surface Chemistry of Amorphous Silica, Zhuravlev Model, Colloidsand Surfaces A: Physiochemical Engineering Aspects 173 (2000) 1-38.

A challenge of known bonding methods is the high temperature requirementof polysilicon TFTs. The demand for higher pixel density, highresolution, and fast refresh rates on hand held displays, notebook anddesktop displays, as well as the wider use of OLED displays, is pushingpanel makers from amorphous silicon TFT backplanes to oxide TFT orpolysilicon TFT backplanes. Because OLEDs are a current driven device,high mobility is desired. Polysilicon TFTs also offer the advantage ofintegration of drivers and other components activation. Highertemperature is preferred for dopant activation, ideally at temperatureover 600° C. Typically, this is the highest temperature in the pSibackplane process.

Another challenge for known bonding methods is bonding to roughsubstrates. Wafer bonding methods with two rigid materials requiresflatness and cleanliness to bring the materials into intimate contact toinitiate bonding. For substrates having rough surfaces, such as etchedinterposers, or non-fusion drawn glass, bonding is easier with a thickermore compliant bonding layer which can elastically or plastically deformto bring the substrates into contact.

SUMMARY

In light of the above, there is a need for a thin sheet-carrier articlethat can withstand the rigors of TFT and flat panel display (FPD)processing, including high temperature processing (without outgassingthat would be incompatible with the semiconductor or display makingprocesses in which it will be used), yet allow the entire area of thethin sheet to be removed (either all at once, or in sections) from thecarrier so as to allow the reuse of the carrier for processing anotherthin sheet. The present specification describes methods to control theadhesion between the carrier and thin sheet to create a temporary bondsufficiently strong to survive TFT and FPD processing (including LTPSprocessing) but weak enough to permit debonding of the sheet from thecarrier, even after high-temperature processing. Such controlled bondingcan be utilized to create an article having a re-usable carrier, oralternately an article having patterned areas of controlled bonding andcovalent bonding between a carrier and a sheet. More specifically, thepresent disclosure provides surface modification layers (includingvarious materials and associated surface heat treatments), that may beprovided on the thin sheet, the carrier, or both, to control bothroom-temperature van der Waals and/or hydrogen bonding, and hightemperature covalent bonding, between the thin sheet and carrier. Evenmore specifically, the room-temperature bonding may be controlled so asto be sufficient to hold the thin sheet and carrier together duringvacuum processing, wet processing, and/or ultrasonic cleaningprocessing. And at the same time, the high temperature covalent bondingmay be controlled so as to prevent a permanent bond between the thinsheet and carrier during high temperature processing, as well as tomaintain a sufficient bond to prevent delamination during hightemperature processing. In alternative embodiments, the surfacemodification layers may be used to create various controlled bondingareas (wherein the carrier and thin sheet remain sufficiently bondedthrough various processes, including vacuum processing, wet processing,and/or ultrasonic cleaning processing), together with covalent bondingregions to provide for further processing options, for example,maintaining hermeticity between the carrier and sheet even after dicingthe article into smaller pieces for additional device processing. Stillfurther, some surface modification layers provide control of the bondingbetween the carrier and sheet while, at the same time, reduce outgassingemissions during the harsh conditions in an TFT or FPD (for exampleLTPS) processing environment, including high temperature and/or vacuumprocessing, for example.

In a first aspect, there is a glass article comprising:

a first sheet having a first sheet bonding surface;

a second sheet having a second sheet bonding surface;

a modification layer having a modification layer bonding surface, themodification layer may comprise organosilicon;

the modification layer bonding surface being in contact with the firstsheet bonding surface, and the second sheet bonding surface beingcoupled with the first sheet bonding surface with the modification layertherebetween, wherein the first sheet bonding surface is bonded with themodification layer bonding surface with a bond energy of less than 600mJ/m² after holding the glass article at 600° C. for 10 minutes in anitrogen atmosphere.

In an example of aspect 1, the first sheet bonding surface is bondedwith the modification layer bonding surface with a bond energy of lessthan 600 mJ/m² after holding the glass article at 700° C. for 10 minutesin a nitrogen atmosphere.

In another example of aspect 1, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energy ofless than 600 mJ/m² after holding the glass article at 750° C. for 10minutes in a nitrogen atmosphere.

In another example of aspect 1, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energy ofless than 450 mJ/m² after holding the glass article at 650° C. for 10minutes in a nitrogen atmosphere.

In another example of aspect 1, the modification layer has a thicknessin the range of 5 nanometers (nm) to 10 microns (μm, or micrometers).

In another example of aspect 1, the modification layer has a thicknessin the range of 10 nm to 500 nm.

In another example of aspect 1, the first sheet is glass having athickness of less than 300 microns.

In another example of aspect 1, the organosilicon is formed bydepositing an organosilane monomer on the first sheet bonding surface.

In a second aspect, there is provided a glass article of aspect 1,wherein the organosilane monomer has a formula (R₁)×Si(R₂)_(y), whereinR₁ is an aryl, alkyl, alkynyl and/or alkenyl and x is 1, 2 or 3, R₂ ishydrogen, halogen, an aryl, alkyl, alkynyl and/or alkenyl, or acombination thereof and y is 1, 2 or 3, wherein R₁ and R₂ are notoxygen.

In an example of aspect 2, R₁ or R₂ is an aryl, phenyl, tolyl, xylyl,naphthyl or a combination thereof.

In another example of aspect 2, R₂ is hydrogen, methyl or a combinationthereof.

In another example of aspect 2, R₁ or R₂ is an aryl.

In another example of aspect 2, R₁ or R₂ is a di-aryl.

The second aspect may be provided alone or in combination with any oneor more of the examples of the second aspect discussed above.

In another example of aspect 1, the organosilicon is formed bydepositing an organosilane monomer on the first sheet bonding surfaceand the organosilane monomer is selected from the group consisting ofphenylsilane, methylphenylsilane, diphenylsilane, methlydiphenylsilaneand triphenylsilane.

In another example of aspect 1, the organosilicon is formed bydepositing an organosilane monomer on the first sheet bonding surfaceand the organosilane monomer being free of an oxygen atom.

In another example of aspect 1, the modification layer is formed bydeposition of a compound selected from the group consisting ofphenylsilicon, methylphenylsilicon, diphenylsilicon,methlydiphenylsilicon and triphenylsilicon.

In another example of aspect 1, the modification layer is not amonolayer.

In another example of aspect 1, the modification layer is a polymerizedamorphous organosilicon.

In another example of aspect 1, the second sheet is in contact with themodification layer.

In another example of aspect 1, the modification layer has an atomicpercent ratio of oxygen to silicon of less than 0.9, wherein the atomicpercent of silicon and oxygen is measured from the modification layerprior to surface modification and being in contact with the first sheetbonding surface.

In another example of aspect 1, the modification layer has an atomicpercent ratio of oxygen to silicon of less than 0.8, wherein the atomicpercent of silicon and oxygen is measured from the modification layerprior to surface modification and being in contact with the first sheetbonding surface.

In another example of aspect 1, the modification layer bonding surfacehas an atomic percent ratio of oxygen to silicon in the range of 1 to 3and an atomic percent ratio of nitrogen to silicon in the range of 0.5to 1.5, wherein the atomic percent of silicon, oxygen and nitrogen ismeasured from the modification layer bonding surface after themodification layer bonding surface is exposed to nitrogen containingreactant to increase the surface energy of the modification layerbonding surface to a range of 55 to 75 mJ/m².

In another example of aspect 1, the modification layer bonding surfacehas an atomic percent ratio of oxygen to silicon of less than 2.5,wherein the atomic percent of silicon and oxygen is measured from themodification layer bonding surface after the modification layer bondingsurface is exposed to nitrogen containing reactant to increase thesurface energy of the modification layer bonding surface to a range of55 to 75 mJ/m².

In another example of aspect 1, the modification layer bonding surfacehas an atomic percent ratio of oxygen to silicon in the range of 1 to 3and an atomic percent ratio of nitrogen to silicon in the range of 2.5to 6.5, wherein the atomic percent of silicon, oxygen and nitrogen ismeasured from the modification layer bonding surface after the glassarticle is held at 700° C. for 10 minutes in nitrogen containingreactant and then the first sheet is separated from the second sheetafter the glass article is cooled to room temperature.

In another example of aspect 1, the modification layer bonding surfacehas an atomic percent ratio of oxygen to silicon of less than 2.6,wherein the atomic percent of silicon and oxygen is measured from themodification layer bonding surface after the glass article is held at700° C. for 10 minutes in nitrogen containing reactant and then thefirst sheet is separated from the second sheet after the glass articleis cooled to room temperature.

In another example of aspect 1, the change in percent of blister area isless than 5 percent after the glass article is subjected to atemperature cycle by heating in a chamber cycled from room temperatureto 600° C. at a rate of 600° C. per minute and held at 600° C. for 10minutes before allowing the glass article to cool to room temperature.

In another example of aspect 1, the change in percent of blister area isless than 1 percent after the glass article is subjected to atemperature cycle by heating in a chamber cycled from room temperatureto 700° C. at a rate of 600° C. per minute and held at 700° C. for 10minutes before allowing the glass article to cool to room temperature.

In another example of aspect 1, the first sheet may be separated fromthe second sheet without breaking the first sheet into two or morepieces after the glass article is subjected to a temperature cycle byheating in a chamber cycled from room temperature to 700° C. at a rateof 600° C. per minute and held at 700° C. for 10 minutes before allowingthe glass article to cool to room temperature.

In another example of aspect 1, there is no outgassing from themodification layer in the temperature range of 300 to 650° C.

The first aspect may be provided alone or in combination with any one ormore of the examples of the first aspect discussed above.

In a third aspect, there is a glass article comprising:

a first sheet having a first sheet bonding surface;

a second sheet having a second sheet bonding surface;

a modification layer having a modification layer bonding surface, themodification layer comprising organosilicon and the modification layernot being a monolayer;

the modification layer bonding surface being in contact with the firstsheet bonding surface, and the second sheet bonding surface beingcoupled with the first sheet bonding surface with the modification layertherebetween, wherein the first sheet bonding surface is bonded with themodification layer bonding surface with a bond energy within the rangeof 150 to 600 mJ/m² over a temperature range of 400 to 600° C., wherebond energy at any particular temperature in the range is measured byholding the glass article at that particular temperature for 10 minutesin a nitrogen atmosphere.

In an example of aspect 3, the first sheet bonding surface is bondedwith the modification layer bonding surface with a bond energy withinthe range of 300 to 400 mJ/m² over a temperature range of 400 to 600°C., where bond energy at any particular temperature in the range ismeasured by holding the glass article at that particular temperature for10 minutes in a nitrogen atmosphere.

In another example of aspect 3, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energywithin the range of 350 to 400 mJ/m² over a temperature range of 400 to600° C., where bond energy at any particular temperature in the range ismeasured by holding the glass article at that particular temperature for10 minutes in a nitrogen atmosphere.

In another example of aspect 3, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energywithin the range of 300 to 400 mJ/m² over a temperature range of 500 to600° C., where bond energy at any particular temperature in the range ismeasured by holding the glass article at that particular temperature for10 minutes in a nitrogen atmosphere.

In another example of aspect 3, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energywithin the range of 500 to 600 mJ/m² over a temperature range of 500 to600° C., where bond energy at any particular temperature in the range ismeasured by holding the glass article at that particular temperature for10 minutes in a nitrogen atmosphere.

In another example of aspect 3, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energywithin the range of 400 to 600 mJ/m² over a temperature range of 450 to750° C., where bond energy at any particular temperature in the range ismeasured by holding the glass article at that particular temperature for10 minutes in a nitrogen atmosphere.

In another example of aspect 3, the first sheet bonding surface isbonded with the modification layer bonding surface with a bond energywithin the range of 300 to 400 mJ/m² over a temperature range of 550 to650° C., where bond energy at any particular temperature in the range ismeasured by holding the glass article at that particular temperature for10 minutes in a nitrogen atmosphere.

In another example of aspect 3, the change in percent of blister area isless than 5 percent after the glass article is subjected to atemperature cycle by heating in a chamber cycled from room temperatureto 600° C. at a rate of 600° C. per minute and held at 600° C. for 10minutes before allowing the glass article to cool to room temperature.

In another example of aspect 3, the change in percent of blister area isless than 1 percent after the glass article is subjected to atemperature cycle by heating in a chamber cycled from room temperatureto 700° C. at a rate of 600° C. per minute and held at 700° C. for 10minutes before allowing the glass article to cool to room temperature.

The third aspect may be provided alone or in combination with any one ormore of the examples of the third aspect discussed above.

In a fourth aspect, there is a method of making a glass articlecomprising:

forming a modification layer on a bonding surface of a second sheet bydepositing an organosilane monomer on the bonding surface of the secondsheet, the modification layer comprising organosilicon and themodification layer having a modification layer bonding surface;

increasing the surface energy of the modification layer bonding surface;and

bonding the bonding surface of a first sheet to the bonding surface ofthe modification layer.

In an example of aspect 4, the surface energy of the modification layerbonding surface is increased by exposure to nitrogen, oxygen, hydrogen,carbon dioxide gas or a combination thereof.

In another example of aspect 4, the surface energy of the modificationlayer bonding surface is increased to equal to or greater than 55 mJ/m²at less than a 60° water/air contact angle.

In another example of aspect 4, the modification layer has a thicknessin the range of 5 nm to 10 microns.

In another example of aspect 4, the first sheet is glass having athickness of 300 microns or less and the second sheet is glass having athickness of 300 microns or greater.

In another example of aspect 4, the modification layer has an atomicpercent ratio of oxygen to silicon of less than 0.9, wherein the atomicpercent of silicon and oxygen is measured from the modification layerprior to surface modification and being in contact with the bondingsurface of the first sheet.

In another example of aspect 4, the modification layer has an atomicpercent ratio of oxygen to silicon of less than 0.8, wherein the atomicpercent of silicon and oxygen is measured from the modification layerprior to surface modification and being in contact with the bondingsurface of the first sheet.

In another example of aspect 4, the modification layer has an oxygen andnitrogen atom content of less than 40 atomic percent of the total amountof atoms present excluding hydrogen, wherein the atomic percent ofoxygen and nitrogen is measured from the modification layer bondingsurface prior to being in contact with the bonding surface of the firstsheet.

In another example of aspect 4, the modification layer bonding surfacehas an atomic percent ratio of oxygen to silicon of 1 to 3 and an atomicpercent ratio of nitrogen to silicon in the range of 2.5 to 6.5, whereinthe atomic percent of silicon, oxygen and nitrogen is measured from themodification layer bonding surface after the glass article is held at700° C. for 10 minutes in nitrogen and then the first sheet is separatedfrom the second sheet after the glass article is cooled to roomtemperature.

In another example of aspect 4, the modification layer bonding surfacehas an atomic percent ratio of oxygen to silicon of less than 2.6,wherein the atomic percent of silicon and oxygen is measured from themodification layer bonding surface after the glass article is held at700° C. for 10 minutes in nitrogen and then the first sheet is separatedfrom the second sheet after the glass article is cooled to roomtemperature.

In another example of aspect 4, the modification layer is formed bydeposition of a compound selected from the group consisting ofphenylsilicon, methylphenylsilicon, diphenylsilicon,methlydiphenylsilicon and triphenylsilicon.

In another example of aspect 4, the modification layer is not amonolayer.

In another example of aspect 4, the modification layer is a polymerizedamorphous arylsilicon.

In another example of aspect 4, the organosilane monomer having formula(R₁)×Si(R₂)_(y), wherein R₁ is an aryl, alkyl, alkynyl and/or alkenyland x is 1, 2 or 3, R₂ is hydrogen, halogen, an aryl, alkyl, alkynyland/or alkenyl, or a combination thereof and y is 1, 2 or 3, wherein R₁and R₂ are not oxygen.

In a fifth aspect, there is provided the method of aspect 4, theorganosilane monomer has a formula (R₁)×Si(R₂)_(y), wherein R₁ is anaryl, alkyl, alkynyl and/or alkenyl and x is 1, 2 or 3, R₂ is hydrogen,halogen, an aryl, alkyl, alkynyl and/or alkenyl, or a combinationthereof and y is 1, 2 or 3, wherein R₁ and R₂ are not oxygen.

In an example of aspect 5, R₁ or R₂ is an aryl, phenyl, tolyl, xylyl,naphthyl or a combination thereof.

In another example of aspect 5, R₂ is hydrogen, methyl or a combinationthereof.

In another example of aspect 5, R₁ or R₂ is an aryl.

In another example of aspect 5, R₁ or R₂ is a di-aryl.

In another example of aspect 5, the organosilane monomer is selectedfrom the group consisting of phenylsilane, methylphenylsilane,diphenylsilane, methlydiphenylsilane and triphenylsilane.

In another example of aspect 5, the organosilane monomer is free of anoxygen atom.

The fifth aspect may be provided alone or in combination with any one ormore of the examples of the fifth aspect discussed above.

In another example of aspect 4, the bonding surface of the first sheetis bonded with the modification layer bonding surface with a bond energyof less than 600 mJ/m² after holding the glass article at 600° C. for 10minutes in a nitrogen atmosphere.

In another example of aspect 4, the bonding surface of the first sheetis bonded with the modification layer bonding surface with a bond energyof less than 600 mJ/m² after holding the glass article at 700° C. for 10minutes in a nitrogen atmosphere.

In another example of aspect 4, the bonding surface of the first sheetis bonded with the modification layer bonding surface with a bond energyof less than 600 mJ/m² after holding the glass article at 750° C. for 10minutes in a nitrogen atmosphere.

In another example of aspect 4, the bonding surface of the first sheetis bonded with the modification layer bonding surface with a bond energyof less than 450 mJ/m² after holding the glass article at 650° C. for 10minutes in a nitrogen atmosphere.

The fourth aspect may be provided alone or in combination with any oneor more of the examples of the fourth aspect discussed above.

The accompanying drawings are included to provide a furtherunderstanding of the principles described, and are incorporated in andconstitute a part of this specification. The drawings illustrate one ormore embodiment(s), and together with the description serve to explain,by way of example, principles and operation of those embodiments. It isto be understood that various features disclosed in this specificationand in the drawings can be used in any and all combinations. By way ofnon-limiting example the various features may be combined with oneanother as set forth in the specification as aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

The above description and other features, aspects and advantages arebetter understood when the following detailed description is read withreference to the accompanying drawings, in which:

FIG. 1 is a schematic side view of an article having carrier bonded to athin sheet with a modification layer therebetween.

FIG. 2 is an exploded and partially cut-away view of the article in FIG.1 .

FIG. 3 is a schematic of an example of a reaction of hydride arylsiliconto form an arylsilicon polymer.

FIG. 4 is a graph of the surface energy of phenylsilicon layers having athickness of 2 microns.

FIG. 5 is a graph of the bond energy and change in percent blister areafor thin glass bonded to phenylsilicon layers having a thickness of 250nm. The phenylsilicon layers were plasma treated with nitrogen prior tobonding the thin glass thereto.

FIG. 6 is a graph of the bond energy and change in percent blister areafor thin glass bonded to methylphenylsilicon layers having a thicknessof 100 nm. The phenylsilicon layers were plasma treated with nitrogenprior to bonding the thin glass thereto.

FIG. 7 is a graph of the bond energy and change in percent blister areafor thin glass bonded to diphenylsilicon layers having a thickness of 30nm. The diphenylsilicon layers were plasma treated with nitrogen priorto bonding the thin glass thereto.

FIG. 8 is a schematic view of a testing setup.

FIG. 9 is a graph of the surface energy for phenylsilicon layers havinga thickness of 250 nm plasma deposited on a glass carrier, and for coverwafers in a test setup according to FIG. 8 .

FIG. 10 is a graph of the surface energy phenylsilicon layers having athickness of 37 nm plasma deposited on a glass carrier, and for coverwafers in a test setup according to FIG. 8 .

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation andnot limitation, example embodiments disclosing specific details are setforth to provide a thorough understanding of various principles andaspects of the present invention. However, it will be apparent to onehaving ordinary skill in the art, having had the benefit of the presentdisclosure, that the present invention may be practiced in otherembodiments that depart from the specific details disclosed herein.Moreover, descriptions of well-known devices, methods and materials maybe omitted so as not to obscure the description of various principlesset forth herein. Finally, wherever applicable, like reference numeralsrefer to like elements.

Directional terms as used herein (e.g., up, down, right left, front,back, top, bottom) are made only with reference to the figures as drawnand are not intended to imply absolute orientation.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment. Itwill be further understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

Provided are solutions for allowing the processing of a thin sheet on acarrier, whereby at least portions of a first sheet, for example, a thinglass sheet, remain “controllably bonded” with a second sheet, forexample a carrier, so that devices processed on the thin sheet may beremoved from the carrier. In order to maintain advantageous surfaceshape characteristics, the carrier is typically a display grade glasssubstrate. Accordingly, in some situations, it is wasteful and expensiveto merely dispose of the carrier after one use. Thus, in order to reducecosts of display manufacture, it is desirable to be able to reuse thecarrier to process more than one thin sheet substrate. The presentdisclosure sets forth articles and methods for enabling a thin sheet tobe processed through the harsh environment of processing lines includinghigh temperature processing and yet still allowing the thin sheet to beeasily removed from the carrier without damage (for example, wherein oneof the carrier and the thin sheet breaks or cracks into two or morepieces) to the thin sheet or carrier, whereby the carrier may be reused.High temperature processing may include processing at a temperature≥400° C., and may vary depending upon the type of device being made. Forexample, high temperature processing may include temperatures up toabout 450° C. as in amorphous silicon or amorphous indium gallium zincoxide (IGZO) backplane processing, up to about 500-550° C. as incrystalline IGZO processing, or up to about 600-650° C. as is typical inLTPS and TFT processes. The articles and methods of the presentdisclosure can be applied to other high-temperature processing, forexample, in the range of 700° to 800° C., and yet still allow the thinsheet to be removed from the carrier without significantly damaging thethin sheet.

As shown in FIGS. 1 and 2 , a glass article 2 has a thickness 8, andincludes a first sheet 20 (e.g., thin glass sheet, for example, onehaving a thickness of equal to or less than about 300 microns, includingbut not limited to thicknesses of, for example, 10-50 microns, 50-100microns, 100-150 microns, 150-300 microns, 300, 250, 200 190, 180, 170,160, 150 140, 130, 120 110 100, 90, 80, 70, 60, 50, 40 30, 20, or 10,microns) having a thickness 28, a modification layer 30 having athickness 38, and a second sheet 10 (e.g., a carrier) having a thickness18.

The glass article 2 is arranged to allow the processing of thin sheet 20in equipment designed for thicker sheets, for example, those on theorder of greater than or equal to about 0.4 mm, for example 0.4 mm, 0.5mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1.0 mm, although the thin sheet20 itself is equal to or less than about 300 microns. The thickness 8,which is the sum of thicknesses 18, 28, and 38, can be equivalent tothat of the thicker sheet for which a piece of equipment, for example,equipment designed to dispose electronic device components ontosubstrate sheets, was designed to process. In an example, if theprocessing equipment was designed for a 700 micron sheet, and the thinsheet had a thickness 28 of 300 microns, then thickness 18 would beselected as 400 microns, assuming that thickness 38 is negligible. Thatis, the modification layer 30 is not shown to scale, but rather it isgreatly exaggerated for sake of illustration only. Additionally, in FIG.2 , the modification layer is shown in cut-away. The modification layercan be disposed uniformly over the bonding surface 14 when providing areusable carrier. Typically, thickness 38 will be on the order ofnanometers, for example 2 nm to 1 micron, 5 nm to 250 nm, or 20 to 100nm, or about 30, 40, 50, 60, 70, 80 or 90 nm. The presence of amodification layer may be detected by surface chemistry analysis, forexample by time-of-flight secondary ion mass spectrometry (ToF Sims).

Carrier 10 has a first surface 12, a bonding surface 14, and a perimeter16. The carrier 10 may be of any suitable material including glass. Thecarrier can be a non-glass material, for example, ceramic,glass-ceramic, silicon, or metal, as the surface energy and/or bondingmay be controlled in a manner similar to that described below inconnection with a glass carrier. If made of glass, carrier 10 may be ofany suitable composition including alumino-silicate, boro-silicate,alumino-boro-silicate, soda-lime-silicate, and may be either alkalicontaining or alkali-free depending upon its ultimate application.Thickness 18 may be from about 0.2 to 3 mm, or greater, for example 0.2,0.3, 0.4, 0.5, 0.6, 0.65, 0.7, 1.0, 2.0, or 3 mm, or greater, and willdepend upon the thickness 28, and thickness 38 when such isnon-negligible, as noted above. In one embodiment, the carrier 10 may bemade of one layer, as shown, or multiple layers (including multiple thinsheets) that are bonded together. Further, the carrier may be of a Gen 1size or larger, for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger(e.g., sheet sizes from 100 mm×100 mm to 3 meters×3 meters or greater).

The thin sheet 20 has a first surface 22, a bonding surface 24, and aperimeter 26. Perimeters 16 (carrier) and 26 may be of any suitableshape, may be the same as one another, or may be different from oneanother. Further, the thin sheet 20 may be of any suitable materialincluding glass, ceramic, or glass-ceramic, silicon wafer, or metal. Asdescribed above for the carrier 10, when made of glass, thin sheet 20may be of any suitable composition, including alumino-silicate,boro-silicate, alumino-boro-silicate, soda-lime-silicate, and may beeither alkali containing or alkali free depending upon its ultimateapplication. The coefficient of thermal expansion of the thin sheet canbe substantially the same as that of the carrier to reduce warping ofthe article during processing at elevated temperatures. The thickness 28of the thin sheet 20 is 300 microns or less, as noted above. Further,the thin sheet may be of a Gen 1 size or larger, for example, Gen 2, Gen3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm×100 mmto 3 meters×3 meters or greater).

The glass article 2 can have a thickness that accommodates processingwith existing equipment, and likewise it can survive the harshenvironment in which the processing takes place. For example, FPDprocessing may include wet ultrasonic, vacuum, and high temperature(e.g., ≥400° C.), processing. For some processes, as noted above, thetemperature may be ≥500° C., ≥550° C., ≥600° C., ≥650° C., ≥700° C., andup to 750° C.

To survive the harsh environment in which article 2 will be processed,the bonding surface 14 should be bonded to bonding surface 24 withsufficient strength so that the first sheet 20 does not separate fromsecond sheet 10. And this strength should be maintained throughout theprocessing so that sheet 20 does not separate from sheet 10 duringprocessing. Further, to allow sheet 20 to be removed from sheet 10 (sothat carrier 10 may be reused), the bonding surface 14 should not bebonded to bonding surface 24 too strongly either by the initiallydesigned bonding force, and/or by a bonding force that results from amodification of the initially designed bonding force as may occur, forexample, when the article undergoes processing at high temperatures,e.g., temperatures of ≥400° C. to ≥750° C. The surface modificationlayer 30 may be used to control the strength of bonding between bondingsurface 14 and bonding surface 24 so as to achieve both of theseobjectives. The controlled bonding force is achieved by controlling thecontributions of van der Waals (and/or hydrogen bonding) and covalentattractive energies to the total adhesion energy which is controlled bymodulating the polar and non-polar surface energy components of sheet 20and sheet 10. This controlled bonding is strong enough to survive FPDprocessing, for instance, including temperatures ≥400° C., and in someinstances, processing temperatures of ≥500° C., ≥550° C., ≥600° C.,≥650° C., ≥700° C., and up to 750° C., and remain de-bondable byapplication of a force sufficient to separate the sheets but not tocause significant damage to sheet 20 and/or sheet 10. For example, theforce should not break either the sheet 20 or sheet 10. Such de-bondingpermits removal of sheet 20 and the devices fabricated thereon, and alsoallows for re-use of sheet 10 as a carrier, or for some other purpose.

Although the modification layer 30 is shown as a solid layer betweensheet 20 and sheet 10, such need not be the case. For example, the layer30 may be on the order of 0.1 nm to 1 μm thick (e.g., 1 nm to 10 nm, 10nm to 50 nm, 100 nm, 250 nm, 500 nm to 1 μm), and may not completelycover the entire portion of the bonding surface 14. For example, thecoverage may be ≤100%, from 1% to 100%, from 10% to 100%, from 20% to90%, or from 50% to 90% of the bonding surface 14. In other embodiments,the layer 30 may be up to 50 nm thick, or in other embodiments even upto 100 nm to 250 nm thick. The modification layer 30 may be consideredto be disposed between sheet 10 and sheet 20 even though it may notcontact one or the other of sheet 10 and sheet 20. In another aspect ofthe modification layer 30, the layer modifies the ability of the bondingsurface 14 to bond with bonding surface 24, thereby controlling thestrength of the bond between the sheet 10 and sheet 20. The material andthickness of the modification layer 30, as well as the treatment of thebonding surfaces 14, 24 prior to bonding, can be used to control thestrength of the bond (energy of adhesion) between sheet 10 and sheet 20.

Deposition of the Modification Layer

Examples of coating methods, for providing a modification layer, includechemical vapor deposition (CVD) techniques, and like methods. Specificexamples of CVD techniques include CVD, low pressure CVD, atmosphericpressure CVD, Plasma Enhanced CVD (PECVD), atmospheric plasma CVD,atomic layer deposition (ALD), plasma ALD, and chemical beam eptitaxy.

The reactive gas mixture used to produce the films may also comprise acontrolled amount of a source gas (carrier gas) selected from hydrogenand inert gases (Group VIII in the periodic table) for example, He, Ar,Kr, Xe. When using low radio frequency (RF) energy, the source gas maycomprise nitrogen. The amount of source gas may be controlled by thetype of gas used, or by the film deposition process conditions.

Surface Energy of the Modification Layer

In general, the surface energy of the modification layer 30 can bemeasured upon being deposited and/or after being further treated, forexample by activation with nitrogen. The surface energy of the solidsurface is measured indirectly by measuring the static contact angles ofthree liquids—water, diiodomethane and hexadecane—individually depositedon the solid surface in air. From the contact angle values of the threeliquids, a regression analysis is done to calculate the polar anddispersion energy components of the solid surface. The theoretical modelused to calculate the surface energy values includes the following threeindependent equations relating the three contact angle values of thethree liquids and the dispersion and polar components of surfaceenergies of the solid surface as well as the three test liquids

$\begin{matrix}{{\gamma_{W}\left( {1 + {\cos\theta_{W}}} \right)} = {4\left( {\frac{\gamma_{W}^{d}\gamma_{S}^{d}}{\gamma_{W}^{d} + \gamma_{S}^{d}} + \frac{\gamma_{W}^{p}\gamma_{S}^{p}}{\gamma_{W}^{p} + \gamma_{S}^{p}}} \right)}} & (1)\end{matrix}$ $\begin{matrix}{{\gamma_{D}\left( {1 + {\cos\theta_{D}}} \right)} = {4\left( {\frac{\gamma_{D}^{d}\gamma_{S}^{d}}{\gamma_{D}^{d} + \gamma_{S}^{d}} + \frac{\gamma_{D}^{p}\gamma_{S}^{p}}{\gamma_{D}^{p} + \gamma_{S}^{p}}} \right)}} & (2)\end{matrix}$ $\begin{matrix}{{\gamma_{H}\left( {1 + {\cos\theta_{H}}} \right)} = {4\left( {\frac{\gamma_{H}^{d}\gamma_{S}^{d}}{\gamma_{H}^{d} + \gamma_{S}^{d}} + \frac{\gamma_{H}^{p}\gamma_{S}^{p}}{\gamma_{H}^{p} + \gamma_{S}^{p}}} \right)}} & (3)\end{matrix}$

where, the subscripts “W”, “D” and “H” stand for water, diiodomethaneand hexadecane, respectively, and the superscripts “d” and “p” stand fordispersion and polar components of surface energies, respectively. Sincediiodomethane and hexadecane are practically non-polar liquids, theabove set of equations reduces to:

$\begin{matrix}{{\gamma_{W}\left( {1 + {\cos\theta_{W}}} \right)} = {4\left( {\frac{\gamma_{W}^{d}\gamma_{S}^{d}}{\gamma_{W}^{d} + \gamma_{S}^{d}} + \frac{\gamma_{W}^{p}\gamma_{S}^{p}}{\gamma_{W}^{p} + \gamma_{S}^{p}}} \right)}} & (4)\end{matrix}$ $\begin{matrix}{{\gamma_{D}\left( {1 + {\cos\theta_{W}}} \right)} = {4\left( \frac{\gamma_{D}^{d}\gamma_{S}^{d}}{\gamma_{D}^{d} + \gamma_{S}^{d}} \right)}} & (5)\end{matrix}$ $\begin{matrix}{{\gamma_{H}\left( {1 + {\cos\theta_{W}}} \right)} = {4\left( \frac{\gamma_{H}^{d}\gamma_{S}^{d}}{\gamma_{H}^{d} + \gamma_{S}^{d}} \right)}} & (6)\end{matrix}$

From the above set of three equations (4-6), by regression analysis, thetwo unknown parameters, dispersion and polar surface energy componentsof the solid surface, γ_(S) ^(d) and γ_(S) ^(p) are calculated. However,with this approach, there is a limiting maximum value up to which thesurface energy of the solid surface could be measured. That limitingmaximum value is the surface tension of water which is 73 mJ/m². If thesurface energy of the solid surface is appreciably greater than thesurface tension of water, the surface will be fully wetted by water,thereby rendering the contact angle approach zero. Beyond this value ofsurface energy, therefore, all calculated surface energy values wouldcorrespond to ˜73-75 mJ/m² irrespective of the real surface energyvalue. For example, if the real surface energies of two solid surfacesare 75 mJ/m² and 150 mJ/m², the calculated values using the liquidcontact angles will be ˜75 mJ/m² for both surfaces.

Accordingly, all contact angles disclosed herein are measured by placingliquid droplets on the solid surface in air and measuring the anglebetween the solid surface and the liquid-air interface at the contactline. Therefore, when a claim is made on the surface energy value beingfrom 55 mJ/m² to 75 mJ/m² it should be understood that these valuescorrespond to calculated surface energy values based on the methoddescribed above and not the real surface energy values which could begreater than 75 mJ/m² when the calculated value approaches that value.

Bonding Energy of the First Sheet to the Modification Layer

In general, the energy of adhesion (i.e., bond energy) between twosurfaces can be measured by a double cantilever beam method or wedgetest. The tests simulate in a qualitative manner the forces and effectson an adhesive bond joint at a modification layer/first sheet interface.Wedge tests are commonly used for measuring bonding energy. For example,ASTM D5041, Standard Test Method for Fracture Strength in Cleavage ofAdhesives in Bonded Joints, and ASTM D3762, Standard Test Method forAdhesive-Bonded Surface Durability of Aluminum, are standard testmethods for measuring bonding of substrates with a wedge.

A summary of the test method includes recording the temperature andrelative humidity under which the testing is conducted, for example,that in a lab room. The first sheet is gently pre-cracked or separatedat a corner of the glass article locally to break the bond between thefirst sheet and the second sheet. A sharp razor can be used to pre-crackthe first sheet from the second sheet, for example, a GEM brand razorwith a thickness of 228±20 microns. In forming the pre-crack, momentarysustained pressure may be needed to fatigue the bond. A flat razorhaving the aluminum tab removed is slowly inserted until the crack frontcan be observed to propagate such that the crack separation increases.The flat razor does not need to be inserted significantly to induce acrack. Once a crack is formed, the glass article is permitted to restfor at least 5 minutes to allow the crack to stabilize. Longer resttimes may be needed for high humidity environments, for example, above50% relative humidity.

The glass article with the developed crack is evaluated with amicroscope to record the crack length. The crack length is measured fromthe end separation point of the first sheet from the second sheet (i.e.furthest separation point from the tip of razor) and the closestnon-tapered portion of the razor. The crack length is recorded and usedin the following equation to calculate bond energy.γ=3t _(b) ² E ₁ t _(w1) ³ E ₂ t _(w2) ³/16L ₄(E ₁ t _(w1) ³ +E ₂ t _(w2)³)  (7)

wherein γ is the bond energy, t_(b) is the thickness of the blade, razoror wedge, E₁ is the Young's modulus of the first sheet 20 (e.g., thinglass sheet), t_(w1) is the thickness of the first sheet, E₂ is theYoung's modulus of the second sheet 10 (e.g., a glass carrier), t_(w2)is the thickness of the second sheet 10 and L is the crack lengthbetween the first sheet 20 and second sheet 10 upon insertion of theblade, razor or wedge as described above.

The bond energy is understood to behave as in silicon wafer bonding,where an initially hydrogen bonded pair of wafers are heated to convertmuch or all the silanol-silanol hydrogen bonds to Si—O—Si covalentbonds. While the initial, room temperature, hydrogen bonding producesbond energies of the order of about 100-200 mJ/m² which allowsseparation of the bonded surfaces, a fully covalently bonded wafer pairas achieved during high temperature processing (on the order of 400 to800° C.) has adhesion energy of about 2000-3000 mJ/m² which does notallow separation of the bonded surfaces; instead, the two wafers act asa monolith. On the other hand, if both the surfaces are perfectly coatedwith a low surface energy material, for example a fluoropolymer, withthickness large enough to shield the effect of the underlying substrate,the adhesion energy would be that of the coating material, and would bevery low leading to low or no adhesion between the bonding surfaces 14,24. Accordingly, the thin sheet 20 would not be able to be processed oncarrier 10. Consider two extreme cases: (a) two standard clean 1 (SC1,as known in the art) cleaned glass surfaces saturated with silanolgroups bonded together at room temperature via hydrogen bonding (wherebythe adhesion energy is about 100-200 mJ/m²) followed by heating to atemperature that converts the silanol groups to covalent Si—O—Si bonds(whereby the adhesion energy becomes 2000-3000 mJ/m²). This latteradhesion energy is too high for the pair of glass surfaces to bedetachable; and (b) two glass surfaces perfectly coated with afluoropolymer with low surface adhesion energy (about 12-20 mJ/m² persurface) bonded at room temperature and heated to high temperature. Inthis latter case (b), not only do the surfaces not bond at lowtemperature (because the total adhesion energy of about 24-40 mJ/m²,when the surfaces are put together, is too low), they do not bond athigh temperature either as there are too few polar reacting groups.Between these two extremes, a range of adhesion energies exist, forexample between 50-1000 mJ/m², which can produce the desired degree ofcontrolled bonding. Accordingly, the inventors have found variousmethods of providing a modification layer 30 leading to a bonding energythat is between these two extremes, and such that there can be produceda controlled bonding sufficient to maintain a pair of glass substrates(for example a glass carrier 10 and a thin glass sheet 20) bonded to oneanother through the rigors of FPD processing but also of a degree that(even after high temperature processing of, e.g. ≥400° C. to 750° C.)allows the detachment of sheet 20 from sheet 10 after processing iscomplete. Moreover, the detachment of the sheet 20 from sheet 10 can beperformed by mechanical forces, and in such a manner that there is nosignificant damage to at least sheet 20, and preferably also so thatthere is no significant damage to sheet 10.

An appropriate bonding energy can be achieved by using select surfacemodifiers, i.e., modification layer 30, and/or thermal or nitrogentreatment of the surfaces prior to bonding. The appropriate bondingenergy may be attained by the choice of chemical modifiers of either oneor both of bonding surface 14 and bonding surface 24, which chemicalmodifiers control both the van der Waal (and/or hydrogen bonding, asthese terms are used interchangeably throughout the specification)adhesion energy as well as the likely covalent bonding adhesion energyresulting from high temperature processing (e.g., on the order of ≥400°C. to 750° C.).

The inventors have found that an article including a thin sheet and acarrier, suitable for FPD processing (including LTPS processing), can bemade by coating the first sheet 20 and or second sheet 10 with anorganosilicon modification layer containing, for example, at least oneof phenylsilicon, methylphenylsilicon, diphenylsilicon,methlydiphenylsilicon and triphenylsilicon or a combination thereof. Themodification layer 30 is not a monolayer. For example, the modificationlayer 30 can be a polymerized amorphous organosilicon as shown in FIG. 3. In other words, the modification layer 30 is not a self-assembledmonolayer as known in the art, but has a thickness greater than 10 nm,and for example greater than 20 nm.

The organosilicon layer may be formed by depositing an organosilanemonomer on the receiving surface. The organosilane monomer can have theformula (R₁)×Si(R₂)_(y), wherein R₁ can be an aryl, alkyl, alkynyland/or alkenyl and x is 1, 2 or 3, and R₂ can be hydrogen, halogen, anaryl, alkyl, alkynyl and/or alkenyl, or a combination thereof and y is1, 2 or 3, and wherein R₁ and R₂ are not oxygen. For example, R₁ or R₂can be an aryl, phenyl, tolyl, xylyl, naphthyl or a combination thereof.In various embodiments R₁ or R₂ is an aryl or a di- or tri-aryl. Inanother example, the organosilane monomer can be selected fromphenylsilane, methylphenylsilane, diphenylsilane, methlydiphenylsilaneand triphenylsilane. In yet another example, the organosilane monomercan be free of an oxygen atom.

The modification layer 30 can provide a bonding surface with a surfaceenergy in a range of from about 55 to about 75 mJ/m², as measured forone surface (including polar and dispersion components), whereby thesurface produces only weak bonding. The desired surface energy requiredfor bonding may not be the surface energy of the initially depositedorganosilicon modification layer. For example, the deposited layer maybe further treated. As initially deposited, and without furtherprocessing, the organosilicon modification layers show good thermalstability. For example, FIG. 4 shows the thermal stability ofphenylsilicon layers having a thickness of 2 microns. As shown, thetotal surface energy (triangular data points represent the total surfaceenergy, diamond data points represent the dispersion component, andsquare data points represent the polar component) does not significantlychange after heating the layers to 500° C. Because of the low surfaceenergy of the tested phenylsilicon layers, e.g., those shown in FIG. 4 ,surface activation may be desirable for bonding to glass. Surface energyof the deposited organosilicon layers can be raised to 76 mJ/m² byexposure to N₂, N₂—H₂, N₂—O₂, NH₃, N₂H₄, HN₃, CO₂, or mixtures thereof,plasma exposure. Table 1 shows the contact angle (for water “W”,hexadecane “HD” and diiodomethane “DIM”) and surface energy (dispersioncomponent “D”, polar component “P”, and total “T”, as measured byfitting a theoretical model developed by S. Wu (1971) to three contactangles of the three aforementioned test liquids W, HD, DIM. See. S. Wu,J. Polym. Sci. C, 34, 19, 1971) of phenylsilicon (“PS”) anddiphenylsilicon (“DPS”) layers. Additionally, Table 1 shows whether thePS or DPS layers were plasma treated or not, and indicates theparticular plasma treatment in the “TREAT” column. Thus, for example,the first line of Table 1 indicates that a PS layer was not plasmatreated, and that had a W contact angle of 74.5, a HD contact angle of2.63, a DIM contact angle of 24.4, and a total surface energy of 47.42mJ/m² of which the dispersion component accounted for 35.69 mJ/m² andthe polar component accounted for 11.73 mJ/m². Similarly, the secondline of Table 1 indicates that a PS layer was plasma treated with N₂—O₂and resultantly had a W contact angle of 13.7, a HD contact angle of3.6, a DIM contact angle of 40.8, and a total surface energy of 74.19mJ/m² of which the dispersion component accounted for 32.91 mJ/m² andthe polar component accounted for 41.28 mJ/m².

TABLE 1 FILM TREAT W HD DIM D P T PS None 74.5 2.63 24.4 35.69 11.7347.42 PS N2—O2 13.7 3.6 40.8 32.91 41.28 74.19 PS N2 19.67 8 34.93 33.8738.95 72.82 DPS None 50.2 8.27 20.6 35.99 23.91 59.9 DPS CO2 8.57 13.8311.53 36.47 40.43 76.9 DPS N2—H2 3.37 22.67 36.97 32.28 43.09 75.37 DPSNH3 3.8 26.37 38.5 31.55 43.48 75.03

As can be seen, the total surface energy of phenylsilicon anddiphenylsilicon layers can be increased to that of about water, or about72-74 mJ/m².

The modification layer achieves the desired bonding of the first sheet20 and the second sheet 10 by having an atomic percent ratio of certainatoms, e.g., oxygen, silicon and nitrogen. X-ray photoelectronspectroscopy (XPS) can be used to determine the surface composition oforganosilicon layers before and after plasma treatment, for example, N₂plasma surface activation. It is notable that XPS is a surface sensitivetechnique and the sampling depth is about several nanometers.

In an example, the atomic percent ratio of the surface composition ofphenylsilicon layers before and after N₂ plasma surface activation isshown in Table 2 below. The phenylsilicon layers as described below weredeposited from organosilicon hydride precursors with a hydrogen carriergas in an Applied Materials P5000 universal CVD apparatus fromphenylsilane and hydrogen with the following process conditions: atemperature of 390° C. with 120 standard cubic centimeters (sccm) ofhelium through the phenylsilane bubbler held at 85° C. and 600 sccm H₂,a pressure of 9 torr, a gap of 210 millimeters and 300 watts (W), 13.56MHz RF energy and a phenylsilane ampoule at 30° C. The deposition rateof the layers was about 1000 nm/min.

The methylphenylsilicon layers were deposited in the same AppliedMaterials P5000 universal CVD apparatus with the following processconditions: a temperature of 390° C. with 200 sccm of helium through themethylphenylsilane bubbler held at 85° C. and 600 sccm H₂, a pressure of9 torr, a gap of 210 millimeters and 450 W RF and a methylphenylsilaneampoule at 80° C.

The diphenylsilicon layers were deposited in the same Applied MaterialsP5000 universal CVD apparatus with the following process conditions: atemperature of 390° C. with 500 sccm He through the diphenylsilanebubbler held at 85° C., 600 sccm H₂, a pressure of 9 torr, a gap of 210millimeters and 300 W RF and the diphenylsilane ampoule at 80° C. It isbelieved that other precursors, for example organosilicon halides, wouldproduce similar results as shown and described herein.

TABLE 2 C N O F Si sum Phenylsilicon 72.7 0.1 9.4 0 17.8 100Phenysilicon + N2 23.1 12.5 45.6 0.4 18.4 100 Surface Activation

As deposited, the modification layer surface of the phenylsilicon layercontains about a 4:1 C:Si atomic percent ratio and about a 0.5:1 O:Siatomic percent ratio. Although no oxygen was deliberately added duringthe deposition process, the as-deposited phenylsilicon layer contained9.4 atomic percent of oxygen. The presence of oxygen in the surfacecomposition of the organosilicon layer may result from scavenging oxygencontaining species from deposition equipment, for example, reactorwalls, impurities in source materials, or even a reaction of the plasmaactivated surface of the modification layer with atmospheric moistureand oxygen after the glass article or sample is removed from thedeposition equipment (e.g., a deposition chamber). Table 2 shows thatafter activation of the modification layer with N₂, nitrogen wasincreased to 12.5 atomic percent as that element was incorporated intothe surface. The O:Si atomic percent ratio increased to about 2.5:1 andthe C:Si ratio decreased to about 1.25:1. The atomic percent presence ofSi remained nearly unchanged after surface treatment of thephenylsilicon layer.

In another example, the atomic percent ratio of the surface compositionof phenylsilicon layers before and after N₂ plasma surface activation isshown in Table 3 below.

TABLE 3 Si—C or Si—O Si—Si silane SiO2 Phenylsilicon 12.7 4.5 0.5Phenysilicon + N2 Surface Activation 1.7 1 15.7

The Si2p surface composition shown in Table 3 shows the Si bonding inthe surface of the as-deposited modification layer is primarily Si—C orSi—Si with only about 25% of the Si being bonded to oxygen. Upon surfaceactivation of the modification layer with N₂, most of the surface oxygenpresent in the modification layer is in the form of SiO₂. Thus, there isa low presence of Si—O bonds after activation.

In another example, the atomic percent ratio of the surface compositionof phenylsilicon layers before and after N₂ plasma surface activation isshown in Table 4 below.

TABLE 4 C—C or C—O— or C═O, pi-pi C—H C—N C—N O═C—O trans. Phenylsilicon69 1.3 0 0.2 2.2 Phenysilicon + N2 11.7 5.3 4 2 0.1 Surface Activation

The C1s surface composition shown in Table 4 shows the C—C, C—H andpi-pi bonding in the as-deposited surface of the modification layer isprimarily C—C or C—H bonding with pi-pi transitions being observed.After N₂ plasma activation, the C—C, C—H and pi-pi bonding in thesurface of the modification layer is significantly decreased and morepolar C—O or C—N species being observed.

In yet another example, the atomic percent ratio of the surfacecomposition of phenylsilicon layers before and after N₂ plasma surfaceactivation is shown in Table 5 below.

TABLE 5 N—C or N═C —NH2 Phenylsilicon Phenysilicon + N2 SurfaceActivation 4.6 7.9

The N₁ surface composition shown in Table 4 shows the nitrogen in theform of N—C, N═C and NH₂ is introduced with N₂ surface activation of themodification layer. For example, 63% of the nitrogen is introduced tothe surface as an amine. These polar surface groups may be responsiblefor plasma activation of the modification layer surface, thereby raisingthe surface energy of the organosilicon modification layer, e.g.,phenylsilicon, to nearly that of glass (i.e. about 74 mJ/m²) and thusallowing bonding with a thin glass sheet.

The individual atomic elements of the surface composition of a depositedmodification methylphenylsilicon (MPS) and diphenlysilicon (DPS) layersbefore and after surface activation with N₂ were measured and reportedbelow in Table 6.

TABLE 6 atomic % C N O F Si MPS 75.0 0.0 8.1 0.2 16.7 MPS + N2 35.3 10.836.9 0.8 16.2 DPS 82.7 0.0 7.4 0.2 9.6 DPS + N2 42.4 14.4 30.2 0.7 12.3

The as-deposited modification layers contain no detectable nitrogen andhave an O:Si ratio of 0.49 for MPS and 0.78 for DPS. As shown, N₂ plasmaactivation incorporates 10.8 atomic percent nitrogen into MPS, 14.4atomic percent nitrogen into DPS, and increases the O:Si ratio of themodification layer surface to over 2.

The surface composition of the modification layers was tested atdifferent stages to determine the changes in surface chemistry. Table 7below shows the impact of annealing with and without N₂ surfaceactivation and bonding to a thin glass sheet.

TABLE 7 B C N O F Al Si Ca Sr DPS as deposited A1 0.77 62.89 0.27 13.810.63 0 21.63 0 0 DPS as deposited A2 0 63.46 0.45 13.42 0.52 0 22.15 0 0DPS unbonded no N2 0 60.81 0 16.46 1.97 0.1 20.66 0 0 treatment 700 C.10 min A3 DPS N2 treated, bonded, 0.45 43.07 5.38 32.62 1.04 0 17.45 0 0annealed 700 C./10 m debonded DPS N2 treated, bonded, 0 45.5 5.71 30.870.96 0 16.83 0.13 0 annealed 700 C./10 m debonded DPS N2 treated,bonded, 2.02 9.41 3.74 57.18 0.46 3.87 22.22 1 0.1 annealed 700 C./10 mdebonded

The DPS layers that were annealed at 700° C. for 10 minutes in N₂without surface activation or bonding showed only slight oxidation andlittle composition change. XPS of the layers after N₂ surfaceactivation, bonding to thin glass, annealing at 700° C. for 10 minutesin N₂, and de-bonding to expose the diphenylsilicon surface in two ofthree locations sampled is similar to that of the N₂ treated DPS surfaceas shown in Table 6. Nitrogen concentration is about half. These resultsare consistent with de-bonding occurring by an adhesive failure at thenitrogen treated surface. In the remaining location, XPS suggests somebare EXG glass is exposed suggesting part of the thin DPS surfacemodification tore away during de-bonding.

Table 8 below shows the elastic modulus (“E”) and hardness (“H”) of 1.1um thick films of phenylsilicon, methylphenylsilicon and diphenylsiliconas measured by nanoindentation.

TABLE 8 E, GPa H, GPa phenylsilicon 16.7 2.3 diphenylsilicon 16.1 2.7methylphenylsilicon 21 3.8

As shown, the elastic modulus measured for the modification layers isabout ten times more than typical polymers such as polyimides, onequarter that of common display glass and significantly less than the 134GPa modulus of amorphous silicon (R. Kuschnereit, H. Fath, A. A.Kolomenskii, M. Szabadi, P. Hess, Mechanical and elastic properties ofamorphous hydrogenated silicon films studied by broadband surfaceacoustic wave spectroscopy, Applied Physics A 1995 (61) 3 269-276.) Thisis consistent with the expected structure and suggests limitedcompliance of the bonding layer.

The use of a surface modification layer 30, together with bondingsurface preparation as appropriate, can achieve a controlled bondingarea, that is, a bonding area capable of providing a room-temperaturebond between sheet 20 and sheet 10 sufficient to allow the article 2 tobe processed in FPD type processes (including vacuum and wet processes),and yet one that controls covalent bonding between sheet 20 and sheet 10(even at elevated temperatures) so as to allow the sheet 20 to beremoved from sheet 10 (without damage to the sheets) after hightemperature processing of the article 2, for example, FPD typeprocessing or LTPS processing. To evaluate potential bonding surfacepreparations, and modification layers with various bonding energies,that would provide a reusable carrier suitable for FPD processing, aseries of tests were used to evaluate the suitability of each. DifferentFPD applications have different requirements, but LTPS and Oxide TFTprocesses appear to be the most stringent at this time. Thus, testsrepresentative of steps in these processes were chosen, as these aredesired applications for the article 2. Annealing at 400° C. is used inoxide TFT processes, whereas crystallization and dopant activation stepsover 600° C. are used in LTPS processing. Accordingly, the followingtesting was carried out to evaluate the likelihood that a particularbonding surface preparation and modification layer 30 would allow a thinsheet 20 to remain bonded to a carrier 10 throughout FPD processing,while allowing the thin sheet 20 to be removed from the carrier 10(without damaging the thin sheet 20 and/or the carrier 10) after suchprocessing (including processing at temperatures ≥400° C. to 750° C.).

Thermal Testing of Bond Energy

The bonding energy of the modification layers to thin glass sheets wasfurther tested under heating conditions. For example, after surfaceactivation, thin glass was observed to bond very well to phenylsilicon,methylphenylsilicon, and diphenylsilicon modification layer bondingsurfaces with a very high bond speed consistent with the high surfaceenergy. And high bond speed has a manufacturing advantage of reducingthe overall processing time, and/or increasing the throughput, toproduce article 2. Thus, initial surface energies that promote rapidbond speeds are advantageous.

FIGS. 5, 6, and 7 , show the evolution of bond energy and change inblister area for thin glass bonded to Corning® Eagle XG® or Lotus XTcarriers coated with nitrogen treated phenylsilicon (i.e. FIG. 5 ),methylphenylsilicon (i.e. FIG. 6 ) and diphenylsilicon (i.e. FIG. 7 ).The bond energy data points in the figures are indicated with a diamondshaped marker with the scale on the left-hand Y-axis, whereas the changein percent blister area is shown by square data points with the scale onthe right-hand Y-axis. The bond energy of thin glass bonded withnitrogen treated phenylsilicon layer having a thickness of 250 nm risesto about 600 mJ/m² at 400° C., and remains near that value untilexcessive blistering is observed at 600° C. Thus, the phenylsiliconsurface modification layer consistently maintains a bond energy lessthan about 600 mJ/m² with the thin glass sheet up to 600° C., i.e.,after holding the glass article at 600° C. for 10 minutes in an inertatmosphere.

Similar results are observed for methylphenylsilicon (FIG. 6 ) with thebond energy of thin glass bonded with nitrogen treatedmethylphenylsilicon near 400 mJ/m² from 300-600° C., with excessiveblistering observed at 600° C. Thus, the methylphenylsilicon surfacemodification layer consistently maintains a bond energy less than about400 mJ/m² (certainly less than 450 mJ/m²) with the thin glass sheet upto 600° C., i.e., after holding the glass article at 600° C. for 10minutes in an inert atmosphere.

As shown in FIG. 7 , the nitrogen treated diphenylsilicon layer exhibitsexcellent bonding energy with a thin glass sheet, for example, the bondenergy remains near 400 mJ/m² (certainly less than 450 mJ/m²) up to 650°C., i.e., after holding the glass article at 650° C. for 10 minutes inan inert atmosphere. Up to 750° C., the diphenylsilicon layerconsistently exhibited a bonding energy less than about 600 mJ/m².Higher temperature evaluation above 750° C. was not possible due tosoftening of the thin glass which had a composition consistent withCorning® EAGLE XG® glass (available from Corning Incorporated, havingoffices in Corning N.Y.).

The foregoing results show that each an N₂ treated phenylsilicon, N₂treated methylphenylsilicon, and N₂ treated diphenylsilicon surfacemodification layer is sufficiently thermally stable to 600° C. and abovefor LPTS processing with a final bond energy less than 600 mJ/m².

Outgassing of the Modification Layer

Polymer adhesives used in typical wafer bonding applications aregenerally 10-100 microns thick and lose about 5% of their mass at ornear their temperature limit. For such materials, evolved from thickpolymer films, it is easy to quantify the amount of mass loss, oroutgassing, by mass-spectrometry. On the other hand, it is morechallenging to measure the outgassing from thin surface treatments thatare on the order of 10 to 100 nm thick or less, for example the plasmapolymer surface modification layers described above, as well as for athin layer of pyrolyzed silicone oil or self-assembled monolayers. Forsuch materials, mass-spectrometry is not sensitive enough. There are anumber of other ways to measure outgassing, however.

A first manner, TEST #1, of measuring small amounts of outgassing isbased on surface energy measurements, and will be described withreference to FIG. 8 . To carry out this test, a setup as shown in FIG. 8may be used. A first substrate, or carrier, 900 having the to-be-testedmodification layer thereon presents a surface 902, i.e., a modificationlayer corresponding in composition and thickness to the modificationlayer 30 to be tested. A second substrate, or cover, 910 is placed sothat its surface 912 is in close proximity to the surface 902 of thecarrier 900, but not in contact therewith. The surface 912 is anuncoated surface, i.e., a surface of bare material from which the coveris made. Spacers 920 are placed at various points between the carrier900 and cover 910 to hold them in spaced relation from one another. Thespacers 920 should be thick enough to separate the cover 910 from thecarrier 900 to allow a movement of material from one to the other, butthin enough so that during testing the amount of contamination from thechamber atmosphere on the surfaces 902 and 912 is minimized. The carrier900, spacers 920, and cover 910, together form a test article 901.

Prior to assembly of the test article 901, the surface energy of baresurface 912 is measured, as is the surface energy of the surface 902,i.e., the surface of carrier 900 having the modification layer providedthereon. The surface energies as shown in FIGS. 9 and 10 , whereintotal, polar, and dispersion, components, were measured by fitting atheoretical model developed by S. Wu (1971) to three contact angles ofthree test liquids; water, diiodomethane and hexadecane. (Reference: S.Wu, J. Polym. Sci. C, 34, 19, 1971).

After assembly, the test article 901 is placed into a heating chamber930, and is heated through a time-temperature cycle. The heating isperformed at atmospheric pressure and under flowing N₂ gas, i.e.,flowing in the direction of arrows 940 at a rate of 2 standard litersper minute.

During the heating cycle, changes in the surface 902 (including changesto the surface modification layer due to evaporation, pyrolysis,decomposition, polymerization, reaction with the carrier, andde-wetting, for example) are evidenced by a change in the surface energyof surface 902. A change in the surface energy of surface 902 by itselfdoes not necessarily mean that the surface modification layer hasoutgassed, but does indicate a general instability of the surfacemodification layer material at that temperature as its character ischanging due to the mechanisms noted above, for example. Thus, the lessthe change in surface energy of surface 902, the more stable themodification layer. On the other hand, because of the close proximity ofthe surface 912 to the surface 902, any material outgassed from surface902 will be collected on surface 912 and will change the surface energyof surface 912. Accordingly, the change in surface energy of surface 912is a proxy for outgassing of the modification layer present on surface902.

Thus, one test for outgassing uses the change in surface energy of thecover surface 912. Specifically, if there is a change in surfaceenergy—of surface 912—of ≥10 mJ/m², then outgassing may be indicated.Changes in surface energy of this magnitude are consistent withcontamination which can lead to loss of film adhesion or degradation inmaterial properties and device performance. A change in surface energyof ≤5 mJ/m² is close to the repeatability of surface energy measurementsand inhomogeneity of the surface energy. This small change is consistentwith minimal outgassing.

During testing that produced the results in FIGS. 9 and 10 , the carrier900, the cover 910, and the spacers 920, were made of Corning® Eagle XG®glass, an alkali-free alumino-boro-silicate display-grade glassavailable from Corning Incorporated, Corning, N.Y., although such neednot be the case. The carrier 900 and cover 910 were 150 mm diameter 0.63mm thick. Generally, the carrier 910 and cover 920 will be made of thesame material as carrier 10 and thin sheet 20, respectively, for whichan outgassing test is desired. During this testing, silicon spacers 0.63mm thick, 2 mm wide, and 8 cm long, were positioned between surfaces 902and 912, thereby forming a gap of 0.63 mm between surfaces 902 and 912.During this testing, the chamber 930 was incorporated in MPT-RTP600srapid thermal processing equipment. The temperature of the chamber wascycled from room temperature to the test limit temperature at a rate of9.2° C. per minute, held at the test limit temperature for 10 minutes,and then cooled at furnace rate to 200° C. After the chamber 930 hadcooled to 200° C., the test article was removed. After the test articlehad cooled to room temperature, the surface energies of each surface 902and 912 were again measured. Thus, by way of example, using the data forthe change in surface energy, tested to a limit temperature of 600° C.,for phenylsilicon (FIG. 9 ), the triangular data points represent totalsurface energy of the cover, the square data points represent the polarcomponent of surface energy for the cover, the diamond data pointsrepresent the dispersion component of surface energy for the cover, thecircle data points represent the total surface energy of thephenylsilicon-coated carrier, the X data points represent the dispersioncomponent of the phenylsilicon-coated carrier, and the pipe-X datapoints represent the polar component of the phenylsilicon-coatedcarrier. The triangular data point at about 25° C. (room temperature)shows a surface energy of 75 mJ/m² (milli-Joules per square meter), andis the surface energy of the bare glass cover, i.e., there has been notime-temperature cycle yet run whereby there has been no deposition ofoutgassed material yet collected on the cover. As outgassed material iscollected on the cover, the surface energy of the cover will decrease. Adecrease in surface energy of the cover of more than 10 mJ/m² isindicative of outgassing from the surface modification material onsurface 104. The data points at 300° C. indicate the surface energy asmeasured after a time-temperature cycle performed as follows: thearticle 901 (having phenylsilicon used as a modification layer on thecarrier 900 to present surface 902) was placed in a heating chamber 930at room temperature, and atmospheric pressure; the chamber was heated toa test-limit temperature of 300° C. at a rate of 9.2° C. per minute,with a N₂ gas flow at two standard liters per minute, and held at thetest-limit temperature of 300° C. for 10 minutes; the chamber was thenallowed to cool to 300° C. at a rate of 1° C. per minute, and thearticle 901 was then removed from the chamber 930; the article was thenallowed to cool to room temperature (without N₂ flowing atmosphere); thesurface energy of surface 912 was then measured and plotted as thepoints (triangle, square, diamond) for 300° C. The remaining data points(triangle, square, diamond) for 250 nm thick phenylsilicon (FIG. 9 , for400° C., 500° C., and 600° C.), as well as the data points (opentriangle, open square, and open diamond) for 37 nm thick phenylsilicon(FIG. 10 ), were then determined in a similar manner. The data points(circle, X, pipe-X in FIG. 9 ) representing surface energy of surface902 for the 250 nm thick phenylsilicon modification layer, and the datapoints (filled triangle, filled square, and filled diamond in FIG. 10 )representing surface energy of surface 902 for a 37 nm thickphenylsilicon modification layer, were determined in a similar manner.

From FIG. 9 , triangular data points, it can be seen that the totalsurface energy of the cover 912 remained about constant at 75 mJ/m²,indicating that no material was collected on cover 912, and consistentwith no outgassing from surface 902. Similarly, over the range of from300° C. to 600° C., the total surface energy of the phenylsiliconmodification layer (circular data points) changed less than about 10mJ/m², consistent with minimal material loss and indicating that themodification layer is very stable.

From FIG. 10 , open triangular data points, it can be seen that thetotal surface energy of the cover 912 remained about constant at about75 mJ/m² (dipping only slightly at 750° C.), up to about 750° C.,indicating that minimal material was collected on cover 912, andconsistent with no outgassing from surface 902. Similarly, over therange of from room temperature to 750° C., the total surface energy ofthe phenylsilicon modification layer (filled triangular data points)changed less than about 10 mJ/m², consistent with minimal material lossand indicating that the modification layer is very stable.

A Second manner, TEST #2, of measuring small amounts of outgassing isbased on an assembled article, i.e., one in which a thin glass sheet isbonded to a glass carrier via a organosilicon modification layer, anduses a change in percent bubble area to determine outgassing. Duringheating of the glass article, bubbles formed between the carrier and thethin sheet that indicate outgassing of the modification layer. Theoutgassing under the thin sheet may be limited by strong adhesionbetween the thin sheet and carrier. Nonetheless, layers ≤10 nm thick(plasma polymerized materials, SAMs, and pyrolyzed silicone oil surfacetreatments, for example) may still create bubbles during thermaltreatment, despite their smaller absolute mass loss. And the creation ofbubbles between the thin sheet and carrier may cause problems withpattern generation, photolithography processing, and/or alignment duringdevice processing onto the thin sheet. Additionally, bubbling at theboundary of the bonded area between the thin sheet and the carrier maycause problems with process fluids from one process contaminating adownstream process. A change in % bubble area of ≥5 is significant,indicative of outgassing, and is not desirable. On the other hand achange in % bubble area of ≤1 is insignificant and an indication thatthere has been no outgassing.

The average bubble area of bonded thin glass in a class 1000 clean roomwith manual bonding is about 1%. The % bubbles in bonded carriers is afunction of cleanliness of the carrier, thin glass sheet, and surfacepreparation. Because these initial defects act as nucleation sites forbubble growth after heat treatment, any change in bubble area upon heattreatment less than 1% is within the variability of sample preparation.To carry out this test, a commercially available desktop scanner withtransparency unit (Epson Expression 10000XL Photo) was used to make afirst scan image of the area bonding the thin sheet and carrierimmediately after bonding. The parts were scanned using the standardEpson software using 508 dpi (50 micron/pixel) and 24 bit RGB. The imageprocessing software first prepares an image by stitching, as necessary,images of different sections of a sample into a single image andremoving scanner artifacts (by using a calibration reference scanperformed without a sample in the scanner). The bonded area is thenanalyzed using standard image processing techniques such asthresholding, hole filling, erosion/dilation, and blob analysis. TheEpson Expression 11000XL Photo may also be used in a similar manner. Intransmission mode, bubbles in the bonding area are visible in thescanned image and a value for bubble area can be determined. Then, thebubble area is compared to the total bonding area (i.e., the totaloverlap area between the thin sheet and the carrier) to calculate a %area of the bubbles in the bonding area relative to the total bondingarea. The samples are then heat treated in a MPT-RTP600s Rapid ThermalProcessing system under N₂ atmosphere at test-limit temperatures of 300°C., 400° C., 500° C. and 600° C., for up to 10 minutes. In certainexamples, as shown in FIG. 7 , the samples were heat treated up totemperatures of 700° C. and 750° C. Specifically, the time-temperaturecycle carried out included: inserting the article into the heatingchamber at room temperature and atmospheric pressure; the chamber wasthen heated to the test-limit temperature at a rate of 9° C. per minute;the chamber was held at the test-limit temperature for 10 minutes; thechamber was then cooled at furnace rate to 200° C.; the article wasremoved from the chamber and allowed to cool to room temperature; thearticle was then scanned a second time with the optical scanner. The %bubble area from the second scan was then calculated as above andcompared with the % bubble area from the first scan to determine achange in % bubble area (A Blister Area (%)). As noted above, a changein bubble area of ≥5% is significant and an indication of outgassing. Achange in % bubble area was selected as the measurement criterionbecause of the variability in original % bubble area. That is, mostsurface modification layers have a bubble area of about 2% in the firstscan due to handling and cleanliness after the thin sheet and carrierhave been prepared and before they are bonded. However, variations mayoccur between materials.

The % bubble area measured, as exemplified by the change in percentbubble area, can also be characterized as the percent of total surfacearea of the modification layer bonding surface not in contact with thefirst sheet 20 bonding surface 24. As described above, the percent oftotal surface area of the modification layer bonding surface not incontact with the first sheet is desirably less than 5%, less than 3%,less than 1% and up to less than 0.5% after the glass article issubjected to a temperature cycle by heating in a chamber cycled fromroom temperature to 500° C., 600° C., 650° C., 700° C. and up to 750° C.at a rate in the range of from about 400 to about 600° C. per minute andthen held at the test temperature for 10 minutes before allowing theglass article to cool to room temperature. The modification layerdescribed herein allows the first sheet to be separated from the secondsheet without breaking the first sheet into two or more pieces after theglass article is subjected to the above temperature cycling and thermaltesting.

The results of the outgassing test are shown in FIGS. 5, 6 and 7 inwhich blistering data is shown as square data points, and is graphedwith the scale as shown on the right-hand Y-axis. FIG. 5 showsblistering data for a 250 nm thick phenylsilicon surface modificationlayer after N₂ plasma treatment and prior to bonding with a thin glasssheet. The phenylsilicon layer exhibited less than 5% change in bubblearea up to about 600° C., which is consistent with no outgassing, butwhich rapidly increased above 600° C. However, up to 500° C., thephenylsilicon layer exhibited less than 1% change in bubble area, againconsistent with no outgassing. Also, as shown by the diamond data pointsgraphed with the scale on the left-hand Y-axis, the phenylsiliconsurface modification layer provides bonding to thin glass up to 600° C.at a bonding energy less than about 600 mJ/m², which permits debondingof the thin glass from the carrier without causing significant damage tothe thin glass sheet.

FIG. 6 shows blistering data for a 100 nm thick methylphenylsiliconsurface modification layer after N₂ plasma treatment and prior tobonding with a thin glass sheet. The methylphenylsilicon layer exhibitedless than 1% change in bubble area up to about 600° C., which isconsistent with no outgassing, but which rapidly increased at atemperature above about 600° C. Also, as shown by the diamond datapoints graphed with the scale on the left-hand Y-axis, themethylphenylsilicon modification layer provides bonding to thin glass upto 600° C. at a bonding energy less than 400 mJ/m², which permitsdebonding of the thin glass from the carrier without causing significantdamage to the thin glass sheet.

FIG. 7 shows blistering data for a 30 nm thick diphenylsiliconmodification layer after N₂ plasma treatment and prior to bonding with athin glass sheet. The diphenylsilicon layer exhibited less than 0.5%change in bubble area at a temperature up to about 700° C. and slightlyabove, which is consistent with no outgassing. Up to 500° C., thediphenylsilicon layer exhibited less than 0.1% change in bubble area,again, consistent with no outgassing. Also, as shown by the diamond datapoints graphed with the scale on the left-hand Y-axis, thediphenylsilicon modification layer provides bonding to thin glass up toat least 750° C. at a bonding energy less than about 600 mJ/m², and upto 650° C. at a bonding energy less than 450 mJ/m², which permitsdebonding of the thin glass from the carrier without causing significantdamage to the thin glass sheet.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the principlesdescribed herein. Thus, it is intended that the scope of the presentdescription cover the modifications and variations that come within thescope of the appended claims and their equivalents.

For example, although the surface modification layer was described asbeing initially deposited onto the sheet 10 (for example a carrier),such need not be the case. Instead, or in addition, the surfacemodification layer may be disposed on sheet 20 (for example a thinsheet).

Further, for example, although the surface modification layer wasdescribed as being one layer, it may be comprised of any suitable numberof layers, for example, two, three, four, or five. In the case where thesurface modification layer has more than one layer, the layer in contactwith the bonding surface of sheet 10 (for example a carrier) need not bethe same composition as the layer in contact with the bonding surface ofthe sheet 20 (for example a thin sheet).

What is claimed is:
 1. A method of making an article comprising: forminga modification layer on a bonding surface of a second sheet bydepositing an organosilane monomer on the bonding surface of the secondsheet, the modification layer comprising organosilicon and themodification layer comprising a modification layer bonding surface;increasing the surface energy of the modification layer bonding surface;and bonding the first sheet to the second sheet with the modificationlayer therebetween, wherein the bonding surface of the first sheetcontacts the bonding surface of the modification layer, wherein theorganosilane monomer comprising a formula ((R₁)×Si(R₂)_(y), wherein: R₁is an item selected from the group consisting of an aryl, alkyl,alkynyl, and alkenyl; x is 1, 2, or 3; R₂ is an item selected from thegroup consisting of hydrogen, halogen, an aryl, alkyl, alkynyl, andalkenyl; y is 1, 2 or 3; and R₁ and R₂ are not oxygen.
 2. The method ofclaim 1, R₁ or R₂ being an aryl, phenyl, tolyl, xylyl, naphthyl or acombination thereof.
 3. The method of claim 1, R₂ being hydrogen, methylor a combination thereof.
 4. The method of claim 1, R₁ or R₂ being anaryl.
 5. The method of claim 1, R₁ or R₂ being a di-aryl.
 6. The methodof claim 1, the organosilane monomer being selected from the groupconsisting of phenylsilane, methylphenylsilane, diphenylsilane,methlydiphenylsilane and triphenylsilane.
 7. The method of claim 1, theorganosilane monomer being free of an oxygen atom.
 8. The method ofclaim 1, the surface energy of the modification layer bonding surfacebeing increased by plasma exposure to nitrogen, oxygen, hydrogen, carbondioxide gas or a combination thereof.
 9. The method of claim 1, themodification layer comprising a thickness in the range of 5 nm to 10microns.
 10. The method of claim 1, the modification layer is formed bydeposition of a compound selected from the group consisting ofphenylsilicon, methylphenylsilicon, diphenylsilicon,methlydiphenylsilicon and triphenylsilicon.
 11. The method of claim 1,the first sheet being glass comprising a thickness of 300 microns orless and the second sheet being glass comprising a thickness of 300microns or greater.